"The scene is truly apocalyptic, it seems like a bomb has hit this important artery which connects Piedmont and Lombardy to the eastern part of Liguria," said La Repubblica's Matteo Pucciarelli, who was filming at the scene.

Rescuers scouring through the wreckage, strewn among shrubland and train tracks, said there were "dozens" of victims, while images from the scene showed an entire carriageway plunged to the ground.

Cars and trucks were tangled in the rubble and nearby buildings damaged by vast chunks of concrete, according to an AFP photographer at the scene.

A fire service spokesperson told AFP that the bridge had mostly fallen on rail tracks 100 metres (yards) below and that "cars and trucks" had fallen with the rubble.

"Firefighters are working together and teams of rescuers and police sniffer dogs have been mobilised," emergency services said on Twitter.

As cars and trucks tumbled off the bridge, Afifi Idriss, 39, a Morrocan lorry driver, just managed to come to a halt in time.

"I saw the green lorry in front of me stop and then reverse so I stopped too, locked the truck and ran," he told AFP.

The green lorry was still on the bridge late evening, stopped just short of the now yawning gap.

A green truck driven came to a halt just in front of a section of the Morandi motorway bridge that collapsed in Genoa on August 14, 2018. Photo: FEDERICO SCOPPA / AFP

"Immense Tragedy"

"I'm following with the utmost apprehension what is happening in Genoa and what looks like it could be an immense tragedy," transport and infrastructure minister Danilo Toninelli said on Twitter Tuesday as news of the bridge's collapse came through.

The cause of the disaster was not immediately clear, although weather services in the Liguria region where Genoa is situated had issued a storm warning Tuesday morning.

The national motorways body said on its website that "maintenance works were being carried out on the base of the viaduct", adding that a crane had been moved on site to assist the work.

Shares in Italian company Atlantia, which runs much of Italy's motorway network including the collapsed stretch of the A10, plunged on the Milan stock exchange after the news.

They were down 9.7 percent at 22.48 euros in mid-afternoon, having earlier been temporarily suspended when they drop exceeded 10 percent.

Salvini's commitments

45-year-old interior minister Matteo Salvini, who is also deputy prime minister and the leader of the nationalist League that governs with the anti-establishment Five Star Movement, said that he was going to find out who was responsible for the tragedy.

"I have gone over this bridge hundreds of times, and I will do everything I can to have the names of those responsible, past and present. It is unacceptable to die like that in Italy," he said.

Eurosceptic Salvini also said that Italy needs to make massive investments in its infrastructure, much of which is dilapidated, alluding to supposed potential restrictions from the European Union should his government unleash funds.

"There is a large part of Italy that needs to be made secure, and if there are external commitments that prevent us from spending the money we need to on the safety of motorways ... we will have to ask ourselves whether we continue to respect these commitments or put the safety of Italians first and foremost," he said.

"Obviously I will choose the second option."

History of collapses

Genoa is located between the sea and the mountains of northwestern Italy.

Its rugged terrain means that motorways that run through the city and the surrounding area are characterised by long viaducts and tunnels.

The Morandi viaduct, completed in 1967, overspans dozens of railway lines as well as an industrial zone housing several factories.

One factory, immediately next to one of the viaducts support columns, was virtually empty on Tuesday due to a national holiday, and seems to have sustained minimal damage.

The incident -- the deadliest of its kind in Europe since 2001 -- is the latest in a string of bridge collapses in Italy, a country prone to damage from seismic activity but where infrastructure generally is showing the effects of economic stagnation.

In March last year a couple were killed when a motorway overpass collapsed on their car near Ancona on the country's Adriatic coast.

A pensioner died in October 2016 when his car was crushed by a collapsing bridge over the SS36 dual carriageway between Milan and Lecco.

That incident was blamed on bureaucratic bungling which led to a fatal delay in the bridge being closed after it was reported to be showing significant cracks.

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